Gyrification Index
Aggregate independently tessellated pial and enclosing-hull areas for the same region and compute a surface gyrification ratio.
Description
A gyrification area ratio compares a folded pial surface with its enclosing hull over the same region.
A gyrification area ratio compares a folded pial surface with its enclosing hull over the same region. More folded area raises the ratio.
The tool returns totalPialAreaMm2 (total pial area mm2); totalHullAreaMm2 (total hull area mm2); gyrificationIndex (gyrification index). Input measurements and model parameters are supplied by the caller; the tool computes the stated summary rather than acquiring those measurements.
When to use Gyrification Index
Use Gyrification Index when you already have pialPatchAreasMm2, hullPatchAreasMm2 and want totalPialAreaMm2, totalHullAreaMm2, gyrificationIndex. This is useful for checking a supplied calculation, documenting a measurement convention, or comparing observations prepared on the same basis.
How to use Gyrification Index and understand its results
- Enter pialPatchAreasMm2, hullPatchAreasMm2 using the field table below. Match the units, ordering and data boundaries described in the calculation.
- Run the tool after checking the stated bounds and matching paired observations or categories. A malformed request gives a tool error rather than a usable measurement.
- Read totalPialAreaMm2, totalHullAreaMm2, gyrificationIndex. Use the calculation and interpretation below to distinguish amounts, ratios, signs and decision flags where applicable.
- Review the supplied parameters and assumptions before using the result in a report or comparing it with another observation.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| pialPatchAreasMm2 | Pial patch areas mm2 | list of number | Required |
| hullPatchAreasMm2 | Hull patch areas mm2 | list of number | Required |
Sum both nonempty nonnegative patch-area lists independently; their tessellations may differ. Require positive hull area and pial total at least the hull total.
gyrification = totalPialArea / totalHullArea The symbols refer to the supplied quantities or generated values described above; unit conversions and comparison boundaries follow the stated implementation.
{
"input": {
"pialPatchAreasMm2": [
3,
5
],
"hullPatchAreasMm2": [
2,
2
]
},
"output": {
"totalPialAreaMm2": 8,
"totalHullAreaMm2": 4,
"gyrificationIndex": 2
}
}Limitations and assumptions
The tool assumes regional correspondence and does not construct a hull or segment cortical surfaces.
Numerical inputs must be finite. The tool checks its declared input shape and calculation constraints; those checks do not verify the quality, calibration or representativeness of the supplied observations.
Alternative or Complementary methods
Cortical Surface Area: Sum triangle areas of a supplied cortical mesh with duplicate-face and index auditing; millimetre coordinates yield square millimetres. Lesion Volume: Integrate lesion voxel fractions using anisotropic voxel dimensions; segmentation and partial-volume probabilities must be supplied.
Methodological background: How to Measure Cortical Folding from MR Images: a Step-by-Step Tutorial to Compute Local Gyrification Index.1
References
-
How to Measure Cortical Folding from MR Images: a Step-by-Step Tutorial to Compute Local Gyrification Index — Schaer et al.; Journal of Visualized Experiments
Similar or alternative tools
- Cortical Surface Area
Sum triangle areas of a supplied cortical mesh with duplicate-face and index auditing; millimetre coordinates yield square millimetres.
- Lesion Volume
Integrate lesion voxel fractions using anisotropic voxel dimensions; segmentation and partial-volume probabilities must be supplied.